1. Field of the Invention
This invention relates to fabrication method and forming mold for multi-fiber optical connector ferrules and particularly to multi-fiber optical connector ferrules that are being produced by means of an aligning mold which has high precision array fiber bores and guide pins laid in an array manner.
2. Description of the Prior Art
Optical fiber has been widely used as a high speed and high capacity communication medium nowadays. Besides for replacing conventional copper-based wire for telephone use, it is particularly desirable for data and image transmission. In optical fiber systems, fiber connector ferrules are essential components for connecting optical fibers. As an optical fiber is a fine and high precision material, making fiber connector ferrule also needs high precision machining process. It takes a lot of micro electromechanical operation to fabricate the fiber connector ferrule.
There are many micro electromechanical fabrication techniques have been developed for producing miniature and high precision components. FIG. 1 illustrates a technique disclosed in U.S. Pat. No. 5,214,730 for a multi-fiber optical connector ferrules module. It mainly includes an upper mold engagement with a lower mold 9 which has a plurality of V-shaped grooves. A plurality of fiber bore forming pins 7 are located in V-shaped grooves for forming fiber bores while a pair of guide bore forming pins 8 are located respectively in another two V-shaped grooves at two lateral sides for forming guide bores.
This technique has the following disadvantages:
1. The fiber bores tend to drift upward during molding process. As a result, the fiber cannot align accurately with the fiber bore when the fiber connector ferrules are produced.
2. The two slant walls of the V-shaped groove will be torn and worn after repetitive fiber movement in the fiber connector ferrule. It will result in not accurate alignment of fiber bore forming pins.
3. The V-shaped grooves are made by mechanical pressing process. It has structural restriction and cannot enhance fiber bore accuracy to a desirable degree.
In order to resolve the problems set forth above, there is another technique being introduced. U.S. Pat. No. 5,786,002 is such an example as shown in FIG. 2. It is called xe2x80x9cGuide Block Assembly For aligning Bore Forming Pins During Molding of Multi-Fiber Optical Connector Ferrulesxe2x80x9d. It has an assembly 10 which includes a plurality of fiber bore blocks 22a-h. Each of the blocks has a fiber bore 32a-h for holding a fiber pin 30 therein. There are a pair of guide bore blocks 24a-b located at two lateral sides. Each of the guide bore blocks 24a-b may hold a guide pin 33. While the technique resolves the V-shaped groove wearing problem set forth above, the guide bore blocks should be made by machining one by one and may result in not accuracy of the fiber bores and their aligning positions.
Moreover conventional micro electromechanical process generally can process only materials of relatively soft property. The molds being used for fabricating the optical connector ferrules have high hardness. Conventional micro electromechanical technique thus is not an efficient process for producing the molds needed.
In view of aforesaid disadvantages, it is therefore an object of this invention to provide a fabrication method and forming mold for multi-fiber optical connector ferrules that uses an integrated mold to obtain high degree of bore accuracy and bores alignment. The diameter of the connector ferrules may be controlled through different fiber mold cores during molding material forming process. The fiber mold core may be made by grinding operation to achieve great precision.
It is another object of this invention to provide a fabrication method and forming mold for multi-fiber optical connector ferrules that uses X-ray LIGA technology to fabricate the mold for obtaining accurate fiber bores and bores alignment.
The mold according to one aspect of this invention includes an aligning mold and two spaced side walls to form a U-shaped member and a middle wall to engage with the side walls to form a rectangular frame. There are a plurality of fiber pins mounted on the middle wall engagement with a plurality of fiber bores formed in the aligning mold. There are also two spaced guide pins on the middle wall engagement with two spaced guide bores formed in the aligning mold. The fiber bores and the guide bores are integrated formed and thus may be made with great precision either for the bore sizes and for their alignment positions.
According to another aspect of this invention, the aligning mold is supported by a substrate. There is an upper mold and a lower mold to cover the rectangular frame between the aligning mold and the middle wall to form a closed mold cavity for forming the fiber connector ferrules.
There are support blocks mounted on the middle wall to hold the fiber pins firmly. The middle wall further has a funnel type inlet to receive molding material into the mold cavity. The guide pins are larger size than the bore pins for holding the mold firmly with adequate strength. The fiber bores and the guide bores are made by X-ray LIGA technology to obtain high precision of bores and alignment positions. The mold core (i.e., the fiber pins) is made by grinding.